It is desirable to disconnect unnecessary devices from an automobile engine when not needed to avoid parasitic drag. For instance, it is common to disconnect air conditioner compressors and cooling fans. Similarly, disconnection of an engine water pump when the engine is cool improves fuel economy and reduces the time necessary for the engine to reach optimal operating temperature.
It is known to use electrical devices to control water pumps. U.S. Pat. No. 6,915,887 describes an electromagnetic type clutch for disconnecting a water pump. At least one manufacturer is producing an electric driven water pump. However, use of electronic devices and controls introduces cost and complexity.
It is known to use thermostatic devices to couple and release relatively rotatable members. U.S. Pat. No. 2,570,515 describes a device for an automobile radiator fan in which jamming rollers with camming projections are engaged with a thermostat to couple and uncouple the driving and driven members. However, once engaged, it is difficult to disengage the jamming roller clutch by applying the minimal force from the thermostat to the projections.
U.S. Pat. No. 6,619,454 describes a disconnect device in which balls are held in place by a keeper that moves axially to release the balls and disconnect the drive. Such a device is designed to disconnect in the event of a malfunction. It is difficult to reconnect the input and output elements under load due to large contact angles and high friction.
Thus there is a long-felt need for a water pump disconnect clutch with low cost and complexity. There is also a need for a water pump disconnect clutch with low engagement friction that can be easily engaged and disengaged with a thermostatic device.